SAN FRANCISCO (CBS SF) – An Excessive Heat Warning took effect in the Bay Area Friday afternoon, as temperatures soared in much of the region.

The National Weather Service issued the warning for most inland areas in the North Bay and East Bay, along with the Santa Cruz Mountains from noon on Friday through 11 p.m. Sunday.

“Dangerously hot conditions with daytime temperatures of 102 to 110 expected,” the weather service said in a statement, with some isolated areas possibly reaching higher temperatures. Overnight hours are expected to provide little relief, as temperatures are only expected to dip into the 70s and 80s.

Temperatures around 9 a.m. Friday were already five to 15 degrees warmer in many locations compared to the same time on Thursday, the weather service reported.

According to KPIX 5 meteorologist Darren Peck, inland East Bay communities reaching the triple digits on Friday include Concord (104), Antioch (101), Danville (105) and Livermore (104).

Other areas set to reach triple digits on Friday include Fairfield (101), Saint Helena in northern Napa County (103), Cloverdale in northern Sonoma County (102), Clearlake (104) and Ukiah (104).

Peck said temperatures are set to be a few degrees hotter on Saturday, with slight cooling on Sunday and highs returning to seasonal norms by Monday.

Meanwhile, the North Bay Valleys and the Santa Clara Valley are under an Excessive Heat Watch, also from Friday afternoon through Sunday night, as temperatures are expected to reach into the mid-90s in cities including San Jose and Santa Rosa.

With hot temperatures expected in much of California for the next few days, the California Independent System Operator (CAISO) has issued a statewide Flex Alert that went into effect at 4 p.m. and will last until 9 p.m. Friday amid concerns about straining the state’s power grid. Californians are urged to take energy saving measures, which include setting thermostats to 78 degrees or higher, avoid using major appliances and keeping unnecessary lights off.

The hot temperatures have also prompted the Bay Area Air Quality Management District to issue a Spare the Air alert for Saturday, as ozone levels are expected to reach unhealthy levels. Air District officials urge Bay Area residents to limit driving and to avoid outdoor exercise during the hottest part of the day.